The present invention generally relates to control program signal demodulating devices, and more particularly to a control program signal demodulating device which demodulates a control program signal from a signal which is reproduced from a rotary recording medium in a reproducing apparatus and transmits this demodulated control program signal to an external device such as a computer which has a discriminating function, and also decodes control commands which are received from the external device and controls the operations of the reproducing apparatus based on the decoded control commands. The rotary recording medium is recorded with a video signal together with an audio signal which is time-sequentially (time-divisionally) multiplexed with the control program signal of the external device, or together with the control program signal which is recorded independently instead of the audio signal.
Heretofore, attempts have been made to more effectively utilize information signals which are recorded on a rotary recording medium (hereinafter simply referred to as a disc). Such attempts include coupling to a disc reproducing apparatus an external device such as a personal computer which has a discriminating function, for example, and controlling the disc reproducing apparatus by the personal computer. For example, the personal computer may be coupled to a reproducing apparatus designed to play a video disc which is recorded with a video signal and audio signals on a spiral track or concentric tracks thereon as variations in geometrical configuration. In this case, it becomes possible to play the video disc in the so-called interactive mode, and this feature enables the video disc to be used in various applications including the recording of educational programs and the recording of games. In addition, when a personal computer is coupled to a reproducing apparatus designed to play an audio disc, it is possible to monitor a picture which is related to a reproduced sound and is generated in the personal computer, at the same time as when the audio signals are reproduced from the audio disc to produce the reproduced sound. Thus, in this case, the picture which is generated simultaneously as the production of the reproduced sound, makes it more interesting and enjoyable for the listener to play the audio disc.
In order to control the disc reproducing apparatus by the personal computer, and generate in the personal computer an information which is related to the signal which is reproduced from the disc, it is of course necessary to load a control program into the personal computer. This control program must be written in a predetermined program language which is in conformance with an interpreter of the personal computer which is used or in conformance with a monitoring device or the like. Hence, it was necessary to prepare a certain number of control programs according to the information content (kind) of the disc. Further, it was only possible to play a disc for which control programs, written in predetermined languages employed in the personal computers which are anticipated on being used, have been prepared, even with respect to the same kind of disc.
In addition, since the video disc did not contain the control program, the control program had to be kept independently by the user. Accordingly, as the number of kinds of the video discs which are kept by the user increased, a corresponding number of control programs had to be kept independently by the user. Thus, there was a problem in that it took up space to keep the large number of control programs. Moreover, when controlling the video disc reproducing apparatus by the personal computer according to the conventional method, there was only a unidirectional path between the personal computer and the video disc reproducing apparatus. In other words, the information from the personal computer was simply supplied to the video disc reproducing apparatus, and it was impossible to detect the state of the video disc reproducing apparatus by the personal computer.
On the other hand, there is a kind of audio disc which is recorded with the control program on an inner peripheral portion thereof, for example. However, in such an audio disc, the recording capacity of the audio signals becomes small, because the signal which represents the control program is recorded on tracks which are distinguished from the tracks which are recorded with the audio signals. Further, a desired operation could not be carried out until all of the control program was loaded into the personal computer. Accordingly, in order to simultaneously enjoy the picture which is generated in the personal computer and the reproduced sound which is obtained by reproducing the audio signals from the audio disc, it was necessary to wait for a predetermined time which was required to reproduce the recorded control program from the audio disc and load the reproduced control program into the personal computer. This was a disadvantage in that it was impossible to immediately start the reproduction of the audio signals. In addition, the memory capacity of the personal computer had to be large, because the personal computer had to store all of the recorded control program at one time. Moreover, the personal computer did not control the audio disc reproducing apparatus, and there was no control of the interactive mode.
There also was a game apparatus which was designed to play a so-called adventure game, by use of the personal computer and a floppy disc which served as an external memory device. However, such a game apparatus could only reproduce animated cartoon type pictures. Further, it required a memory capacity in the order of 4 kilo-bytes to obtain one still picture. Thus, if a compact type floppy disc which only has one recording side was employed, for example, only 40 still pictures could be reproduced from such a compact floppy disc. In addition to the video signal related to the still picture, it was necessary to store the control program described before.